In the text which follows, the term microstructure is to be understood as meaning both microelectronic and micromechanical structures.
Although they can in principle be applied to any desired integrated circuits, the present invention and the problems on which it is based are explained with reference to integrated memory circuits in silicon technology.
Introduction of the 110 nm memory technology and most recently introduction of the 90 nm memory technology are associated with the lithography being switched over to the 193 nm generation in order to enable the extremely small features required to be reproduced.
According to the Rayleigh criterion, the introduction of ever shorter wavelengths leads to a restriction in the focus depth, and therefore it is necessary to use extremely thin photoresist layers of the order of magnitude of 100 nm and wafer surfaces which are as planar as possible in front of the respective lithography plane.
In particular the patterning of active areas in DRAM technologies by means of an STI (Shallow Trench Isolation) etch with a minimum feature size of 90 nm and below imposes severe demands, since the problem of patterning using the ever smaller photoresist thicknesses cannot be solved adequately using conventional solution approaches.